In order to bring a wheeled vehicle to a stop, a vehicle's braking system converts the kinetic energy of the moving vehicle to heat. This friction is generated when a brake pad or shoe is forced into contact with a brake disc or drum. The friction between the two components will eventually dissipate all of the kinetic energy and the vehicle will come to a complete stop.
Some vehicles are equipped with an anti-lock braking system and wheel speed sensors (e.g., toothed encoders) at each wheel to detect whether application of the brakes causes any of the wheels to skid, i.e., to determine whether a wheel begins sliding over a surface while the vehicle continues moving. If the anti-lock braking system determines that a wheel is skidding, the anti-lock braking system decreases or pulses the brake pressure to allow that wheel to rotate again as the vehicle is slowing.